CSS Laboratories SB-6862, Technical Reference

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17 SB-6862
Controller 1 Controller 2
Channel 0 - Spare Channel 4 - Cascade
for Controller 1
Channel 1 - SDLC Channel 5 - Spare
Channel 2 - Diskette Channel 6 - Spare
Channel 3 - Spare Channel 7 - Spare
Note: IRQ9, IRQ10, IRQ11, IRQ12, IRQ15, IRQ3, IRQ4,
IRQ5 and IRQ7 can be redirected to PCI add-in boards.
The PCI standard has a 4-IRQ limitation. Some PCI add-in
boards do not require IRQs. Some can share an IRQ with
another board of the same model and manufacture. Check the
add-in board’s docmentation for IRQ information.
Direct Memory Access
The system supports seven DMA channels:
The first DMA controller holds channels 0 through 3. These
channels support 8-bit data transfers between 8-bit I/O
adapters and 8- or 16-bit system memory. Each channel can
transfer data in 4 KB blocks.
The second DMA controller holds channels 4 through 7.
Channel 4 cascades channels 0 through 3 to the
microprocessor. Channel 5, 6 and 7 support 16-bit data
transfers between 16-bit I/O adapters and 16-bit system
memory. These DMA channels can transfer data throughout
the 16 MB system-address space in 128 KB blocks.
Channel 5, 6 and 7 cannot transfer data on odd byte
boundaries.